1. Field of Invention
The present invention relates to an optical fiber current transformer, and more particularly to an optical fiber current transformer with two-temperature source compensation mode.
2. Description of Related Arts
The optical fiber current transformer is based on the Ampere's law and Faraday magneto-optical effect. It can indirectly measure the current value by measuring the phase difference, induced by the current magnetic field, between two orthogonally polarized light beams transmitting in the sensing fiber.
For optical fiber current transformers applied in the electrical power network, the environment temperature effects on the measured current value may include
1. The variation of magneto-optical coefficient with the change of temperature;
2. The retardation of fiber optic wave plate changes with the change of temperature;
3. The internal strain in the sensing fiber may vary with the change of temperature;
4. The half-wave voltage, Vπ, of phase modulators varies with the change of temperature;
5. The temperature effect of the analog circuit devices.
Therefore, the measurement of current performed by traditional optical fiber current transformers is low-accuracy due to the temperature effects of the sensor systems.